Troubleshooting: AP Does Not Switch Links In a Timely Manner

Common Causes

• The dual-link backup function is disabled on the active AC.
• The IP address of the standby AC is not configured on the active AC or the configured IP address of the standby AC is different from the actual one.
• The standby AC is not started properly.
• The dual-link backup function is disabled on the standby AC.

Troubleshooting Flowchart

Troubleshooting Procedure (Web NMS)

1. Check whether the dual-link backup function is enabled on the active AC.
   • If the dual-link backup function is enabled, go to step 2.
   • If the dual-link backup function is not enabled, enable the dual-link backup function.

     Select the active AC and choose Configuration > Backup Settings > Backup Settings > Backup Configuration > Dual-link hot backup to check whether the dual-link backup function is enabled. If the dual-link backup function is not enabled, enable it.

2. Check whether the IP address of the standby AC configured on the active AC is correct.
   1. Check the configured IP address of the standby AC on the active AC according to step 1.
   2. Check the actual IP address of the standby AC.

      Select the standby AC and choose Configuration > AC Config > Basic Config > AC Configuration to check the IP address of the standby AC. If you select IP Address for AC source address, the value is displayed. If you select VLANIF for AC source address, check the IP address of the VLANIF interface.

   3. Check whether the IP addresses are the same.
      • If the IP addresses the same, go to step 3.
      • If the IP addresses are different, change the configured IP address of the standby AC on the active AC.

3. Check whether the standby AC functions properly.

   When the standby AC and active AC fail, the AP cannot be switched to the standby AC and cannot go online.

   • If the standby AC works properly, go to step 4.
   • If the standby AC does not work properly, troubleshoot the fault according to the actual situation.

4. Check whether the dual-link backup function is enabled on the standby AC. The procedure is the same as that in step 1.
   • If the dual-link backup function is enabled, go to step 5.
   • If the dual-link backup function is not enabled, enable the dual-link backup function on the standby AC.

5. Collect the following information and contact Huawei technical support personnel.
   • Results of the preceding troubleshooting procedure
   • Configuration file, logs, and alarms of the device

Troubleshooting Procedure (CLI)

1. Check whether the dual-link backup function is enabled on the active AC.
   • If the dual-link backup function is enabled, go to step 2.
   • If the dual-link backup function is not enabled, enable the dual-link backup function.

     Run the display wlan ac protect command on the active AC, check whether the dual-link backup function is enabled. If the dual-link backup function is not enabled, run the ac protect enable command to enable the dual-link backup function.

     [AC20] display ac protect  
      ------------------------------------------------------------ 
      Protect state             : disable  
      Protect AC                : -  
      Priority                  : 0  
      Protect restore           : enable  
      Coldbackup kickoff station: disable 
      ------------------------------------------------------------ 

2. Check whether the IP address of the standby AC configured on the active AC is correct.
   1. Check the configured IP address of the standby AC on the active AC according to step 1.
   2. Check the actual IP address of the standby AC.

      Run the display capwap configuration command on the standby AC to check the IP address. Check the value of Source ip-address.

      [AC20] display capwap configuration 
       ------------------------------------------------------------ 
       Source interface                            : - 
       Source ip-address                           : 10.1.1.111 
       Echo interval(seconds)                      : 25  
       Echo times                                  : 6  
       Control priority(server to client)          : 7  
       Control priority(client to server)          : 7  
       Control-link DTLS encrypt                   : disable  
       DTLS PSK value                              : ******  
       PSK mandatory match switch                  : enable 
       Control-link inter-controller DTLS encrypt  : disable 
       Inter-controller DTLS PSK value             : ****** 
       IPv6 status                                 : disable  
       ------------------------------------------------------------ 

   3. Check whether the IP addresses are the same.
      • If the IP addresses are the same, go to step 3.
      • If the IP addresses are different, run the ac protect protect-ac command to change the IP address of the standby AC that is configured on the active AC.

3. Check whether the standby AC functions properly.

   If the standby AC becomes faulty, the AP fails to go online through the standby AC when the active AC becomes faulty.

   • If the standby AC works properly, go to step 4.
   • If the standby AC does not work properly, troubleshoot the fault according to the actual situation.

4. Check whether the dual-link backup function is enabled on the standby AC. The procedure is the same as that in step 1.
   • If the dual-link is enabled, go to step 5.
   • If the dual-link is not enabled, enable the dual-link on the standby AC.

5. Collect the following information and contact Huawei technical support personnel.
   • Results of the preceding troubleshooting procedure
   • Configuration file, logs, and alarms of the device

Troubleshooting Cases

Problem description:

The APs connect to AC1 and AC2. AC1 and AC2 function as the active and standby ACs respectively. When AC1 becomes faulty, the AP that originally goes online on AC1 does not switch to AC2.

Networking:

Fault analysis:

Check AC1 and AC2 configurations. The dual-link backup function is disabled on AC1. Therefore, the AP will not switch to AC2 even if the correct IP address of AC2 is configured on AC1.

Procedure:

Check whether the dual-link backup function is enabled on AC1.

The dual-link backup function is disabled on AC1. As a result, the AP does not set up a link with AC2 or go online on AC2 when AC1 becomes faulty.

Summary:

• This fault is usually caused by a link establishment failure. In actual scenarios, check whether both links are set up successfully first.
• It is difficult to determine whether dual links are set up in a complex networking environment. If such a fault occurs, troubleshoot the fault according to the listed common causes. For details, see Troubleshooting: Dual Links Cannot Be Set Up.